Isolation and characterization of revertants from fourteen herpes simplex virus type 1 (strain 17) temperature-sensitive mutants.

The isolation of spontaneous non-temperature-sensitive revertants of herpes simplex virus type 1 (HSV-1) (strain 17) ts mutants, following a single round of selection at non-permissive temperature, is reported. The distinction between total and incomplete reversion was assessed by the wild-type performance of non-ts revertants in three aspects of HSV infection: (i) virus growth, (ii) induction of HSV-specified enzyme activities (where appropriate) and (iii) the gel profile of infected cell polypeptides. Wild-type behaviour was taken to indicate total reversion, while less than wild-type performance in any test indicated incomplete reversion. Only five of 19 HSV-1 mutants (ts L, U, X, R and G syn) examined for reversion of the ts lesion failed to yield non-ts revertants; these mutants may well contain multiple mutations. Total reversion was obtained with mutants ts K, F, E, S, M, N and I and incomplete reversion with the mutants ts D, T, B, P, A, W, F, H and possibly K. Thus, both total and incomplete revertants of ts F (and possibly ts K) were obtained. Some conclusions concerning the relative importance of individual polypeptide bands have been drawn from these studies. Within our sample in the revertant profiles Vmw 175, 155, 114, 65/64, 43, 40, 39, 30, 28, 21 and 16.5K always returned to wild-type levels; Vmw 273, 100, 67 and 38/37K almost always regained wild-type intensity but polypeptides Vmw 122, 117, 82/81, 57, 51, 27 and 12.5K were frequently not made in wild-type amounts.